The present invention relates generally to an improved unloading device, such as an unloading device from a load retaining vehicle such as a manure spreader or forage box, and being particularly adapted for use in combination with a manure spreader having beater or spreader means disposed at the rear thereof. Means, in the form of a load pushing gate, are provided for transporting the load to the beater means for ultimate spreading, with the gate being movable at a controllably variable rate.
Traditionally, manure spreaders employ a load transport means for delivering the load to the beaters wherein the transport means is essentially in the form of a floating bed or the like. The power for carrying the bed rearwardly is normally provided by a ground engaging wheel, or may, in certain instances, be provided by any alternate power source.
One disadvantage of such typical spreader devices using a load pushing or transporting means operating at a constant rate is that it is difficult to compensate for spreading of both heavy loads and light loads. In other words, as the load depth becomes greater, the load transporting means should reasonably be operated more slowly in order that the material to be spread will be delivered to the beaters at a uniform rate. On the other hand, for light loads, means should be provided to transport the load to the beaters at a relatively rapid rate in order to avoid consumption of both time and energy, while continuing to distribute the load at a relatively even rate.
In the past, efforts have been undertaken to provide false end-gates or other load pushing means for spreader boxes, however these structures have not been totally satisfactory. Frequently, the cables or other devices utilized to controllably move the load transporting means are external of the box and as such present an obstacle to free movement of the structure. Also, these moving cables tend to present a hazard inasmuch as they frequently are permitted to remain unguarded, the hazard continuing to exist due to tensile stresses occurring even in the absence of rapidly moving cable or the like. In certain instances, single or dual hydraulic cylinders have been utilized to directly move a false end-gate or other load pushing means in a spreader box, however variations in loading has caused differential stresses to occur, and thus contribute to a canting of the load pushing means during operation. Also, such cylinder means, when utilized alone, normally requires the utilization of an extremely long box, due to the length requirement of the cylinder and ram when fully retracted. Such length requirements further contribute to improper draw bar loading, thereby rendering it impossible to deliver an appropriate proportion of the load to the tractor draw bar.
A problem frequently encountered with ordinary cable actuated load pushing means is the inability of the pushing means to function while remaining disposed transversely to the axis of the box. Frequently, variations in load depth and densities cause the load transporting means such as a load pushing gate to become canted and otherwise bind during the load pushing or transporting operation. Any twisting of the load transporting gate frequently results in breaking of cables or bending of hydraulic rams which may be utilized to controllably move the cables.